Project Summary To advance the ongoing NIH funded research at UC, Santa Barbara an Abberior Instruments STED confocal microscopy system for super-resolved images of fixed or live 3D samples will be acquired. The proposed instrument will surpass the conventional optical resolution limits of confocal microscopy and will allow detection of structures down to 50 nanometers resolution in the sample plane and 100 nanometers in the depth direction. The STED super-resolution method uses stimulated emission depletion, an all-optical method, to resolve details smaller than the diffraction limit. In the STED method a standard excitation beam is overlapped and aligned with a longer wavelength torus shaped beam that red-shifts the fluorescence emission of fluorescent molecules away from the standard emission peak. Only the remaining fluorescence at the center of the torus emits in the normal emission range and is detected. The detected center spot can be made arbitrarily small limited by laser intensity and fluorophore photobleaching. After exploring upgrades and testing numerous systems, the researchers found that the Abberior Instrument STED system was the best suited for supporting their research projects. From preliminary data the STED system was found to successfully achieve super resolution in a number of the Users samples. The increased spatial resolution is critically needed to further their research goals including: identification of individual tau condensates, resolving unmyleinated axons, tracing serotonergic fibers, colocalizing the PKD genetic disease product, and colocalizing protein-protein interactions. To enable the best use and long-term maintenance of the instrument the microscope would be located in a full time staffed shared-use facility and will be available to all researchers on campus. The instrument would enable not only ongoing campus research but also the development of resources with broader impact.